Systems and methods for reducing the risk of proximal junctional kyphosis using a bone anchor or other attachment point

ABSTRACT

Systems and methods for reducing the risk of PJK, PJF, and other conditions are disclosed herein. In some embodiments, a longitudinal extension can be added to a primary fixation construct to extend the construct to one or more additional vertebral levels. The extension can be attached to a first attachment point, such as a bone anchor implanted in a vertebra that is superior to the primary construct. The extension can also be attached to a second attachment point, such as a component of the primary construct or an anatomical structure disposed inferior to the first attachment point. The extension can be more flexible than the primary construct and/or can limit motion to a lesser degree than the primary construct, thereby providing a more-gradual transition from the instrumented vertebrae to the natural patient anatomy adjacent thereto. The extension can be placed with little or no soft tissue disruption.

FIELD

Systems and methods for reducing the risk of proximal junctionalkyphosis (PJK), proximal junctional failure (PJF), and other conditionsare disclosed herein.

BACKGROUND

There are a number of spinal surgeries in which a fixation orstabilization construct is implanted in a patient and attached to thepatient's spine. For example, a typical posterior fixation construct mayinclude one or more longitudinal spinal rods attached to multiple of thepatient's vertebrae by respective bone anchors. Exemplary bone anchorscan include pedicle or lateral mass screws, hooks, wires, and so forth.The implanted construct extends along a segment of the spine between anuppermost instrumented vertebra (UIV), i.e., the most-superior ormost-cranial vertebra to which the construct is attached, and alowermost instrumented vertebra (LIV), i.e., the most-inferior ormost-caudal vertebra to which the construct is attached.

One complication that can arise with these surgeries is an undesireddegree of kyphosis at or above the UIV. Proximal junctional kyphosis(PJK) is typically defined as a proximal junctional sagittal Cobb anglegreater than 10 degrees, or at least 10 degrees greater than in apre-operative measurement. It is estimated that between 5% and 46% ofadult spine patients suffer from some form of PJK, with most cases beingdiagnosed weeks or months after the surgery. In some cases, proximaljunctional failure (PJF) can occur. PJF may be characterized by (i)post-operative fracture of the UIV or the vertebra superiorly-adjacentthereto (UIV+1), (ii) UIV implant failure, (iii) PJK increase greaterthan 15 degrees, and/or (iv) a need for proximal extension of the fusionor the construct within 6 months of the surgery. FIG. 1 is a sagittalview of a patient spine S in which PJK/PJF has occurred above the UIVafter surgery to implant a fixation construct C. Patients who sufferfrom PJK or PJF may experience increased pain, neurologic deficit, orambulatory difficulties, and may be faced with revision surgery and theexpenses and risks associated therewith.

SUMMARY

Systems and methods for reducing the risk of PJK, PJF, and otherconditions are disclosed herein. In some embodiments, a longitudinalextension can be added to a primary fixation construct to extend theconstruct to one or more additional vertebral levels. The extension canbe attached to a first attachment point, such as a bone anchor implantedin a vertebra that is superior to the primary construct. The extensioncan also be attached to a second attachment point, such as a componentof the primary construct or an anatomical structure disposed inferior tothe first attachment point. The extension can be more flexible than theprimary construct and/or can limit motion to a lesser degree than theprimary construct, thereby providing a more-gradual transition from theinstrumented vertebrae to the natural patient anatomy adjacent thereto.The extension can be placed with little or no soft tissue disruption.

In some embodiments, a surgical method can include attaching a primaryconstruct to a spine of a patient, the primary construct extendingbetween an uppermost instrumented vertebra (UIV) and a lowermostinstrumented vertebra (LIV); attaching a flexible longitudinal extensionto a first attachment point, the first attachment point being disposedsuperior to the UIV of the primary construct; positioning the extensionrelative to the patient's spine; and attaching the extension to a secondattachment point, the second attachment point being disposed at orinferior to the UIV of the primary construct.

The first attachment point can include a bone anchor implanted in avertebra disposed superior to the UIV of the primary construct. Thefirst attachment point can be at least two vertebral levels superior tothe UIV of the primary construct. The second attachment point caninclude a rigid spinal rod of the primary construct. The extension canhave a stiffness that is greater than a stiffness of patient anatomysuperior to the UIV of the primary construct and that is less than astiffness of the primary construct. The extension can have a degree ofspinal motion restriction that is greater than that of patient anatomysuperior to the UIV of the primary construct and less than that of theprimary construct. The extension can limit flexion of the spine withoutcompletely preventing such flexion. In some embodiments, vertebraeinstrumented with the primary construct are fused to one another orprepared for such fusion and vertebrae to which the primary construct isextended by the extension are not fused or prepared for fusion. Theprimary construct can include a rigid spinal rod attached to first andsecond vertebrae by respective bone anchors. The method can includeforming a primary incision through which the primary construct isimplanted. The primary incision can terminate at a location inferior toa vertebra (UIV+1) that is superior-adjacent to the UIV of the primaryconstruct. The extension can include a polymeric tether. The extensioncan exert extension forces on the patient's spine. The first attachmentpoint can be a rib. The first attachment point can be a soft tissuestructure of the patient. The extension can be attached to the firstattachment point by a hook or a clamp. The extension can be attached tothe first attachment point by a bone anchor through which the extensionis threaded. Attaching the extension to the first attachment point caninclude driving a bone anchor into bone with the extension extendingfrom the bone anchor and through a shaft of a driver instrument.

Positioning the extension can include passing the extension through asecondary incision disposed superior to a primary incision through whichthe primary construct is implanted. Positioning the extension caninclude passing the extension through the secondary incision and thenpushing and/or pulling the extension in an inferior direction towardsthe primary construct, passing the extension beneath the skin and/orsoft tissue disposed intermediate to the secondary incision and theprimary construct. Positioning the extension can include passing aninserter instrument through the primary incision in a superior directiontowards the secondary incision, contacting the extension with theinserter instrument, and pulling the extension in an inferior directionusing the inserter instrument. Positioning the extension can includepassing an inserter instrument through the secondary incision, couplingthe extension to the inserter instrument, and pushing the inserterinstrument and the extension coupled thereto in an inferior directiontowards the primary construct, beneath the skin and/or soft-tissuedisposed intermediate to the secondary incision and the primaryconstruct. Positioning the extension can include inserting the extensionthrough a primary incision through which the primary construct isimplanted, and passing the extension in a superior direction towards thefirst attachment point while guiding the extension beneath the skinand/or soft tissue disposed intermediate to the first attachment pointand the primary incision.

The extension can be attached to the second attachment point by aconnector. The connector can clamp the extension to a spinal rod or abone screw of the primary construct. The extension can be a firstextension and the method can include placing a second extension on acontralateral side of the spinal midline from the first extension.Positioning the extension can include passing the extension superiorlyfrom a primary incision through which the primary construct is implantedto the first attachment point, the extension passing beneath the skinand/or soft tissue of the patient, and attaching the extension to thefirst attachment point can include hooking a hook attached to theextension onto the first attachment point or clamping a clamp attachedto the extension onto the first attachment point. In some embodiments,no portion of the extension is disposed anterior to any lamina of thepatient's spine when the extension is attached to the first and secondattachment points.

In some embodiments, a surgical method can include forming a primaryincision in a patient; attaching a primary construct to the patient'sspine via the primary incision; forming a secondary incision in thepatient at a location superior to the primary incision; inserting a boneanchor through the secondary incision with an elongate flexible tetherattached to the bone anchor; driving the bone anchor into bone at afirst attachment point, thereby attaching the tether to the firstattachment point while a portion of the tether extends through thesecond incision to a location outside the patient; tunneling the tetherbeneath soft tissue disposed intermediate to the primary incision andthe secondary incision; and attaching the tether to the primaryconstruct via the primary incision.

Tunneling the tether can include inserting an inserter instrumentthrough the secondary incision and pushing the instrument inferiorlytowards the primary incision. The method can include grasping a leadingend of the inserter instrument via the primary incision and pulling theinserter instrument through the primary incision. The tether can beattached to the inserter instrument and can be carried along the samepath as the inserter instrument, thereby positioning the tether suchthat it extends along the patient's spine between the first attachmentpoint and the primary construct.

In some embodiments, a surgical system can include a primary constructcomprising a rigid spinal fixation rod and first and second bone anchorsconfigured to attach the spinal rod to first and second vertebrae; anelongate flexible tether attached to a tether anchor; a driverinstrument for driving the tether anchor into bone while the tetherextends from the tether anchor; and a connector configured to clamp thetether to the spinal rod of the primary construct.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sagittal view of the spine of a human patient suffering fromPJK/PJF;

FIG. 2A is a perspective view of a human spine with a primary constructand a longitudinal extension attached thereto;

FIG. 2B is a flow chart of a surgical method;

FIG. 3A is a perspective view of a human spine with a bone anchor beingattached thereto;

FIG. 3B is a perspective view of a driver instrument being removed fromthe bone anchor of FIG. 3A;

FIG. 3C is a perspective view of an inserter instrument inserted througha secondary incision;

FIG. 3D is a perspective view of the inserter instrument pulling atether through the patient;

FIG. 3E is a perspective view of the tether being attached to a spinalrod by a connector;

FIG. 4 is a perspective view of an extension with a hook being attachedto a patient;

FIG. 5 is a perspective view of an extension with a clamp being attachedto a patient;

FIG. 6A is a perspective view of a connector that attaches a spinal rodto a tether;

FIG. 6B is an exploded perspective view of the connector, tether, androd of FIG. 6A;

FIG. 6C is a front view of a body of the connector of FIG. 6A;

FIG. 6D is a side view of the body of FIG. 6C;

FIG. 6E is a sectional perspective view of the body of FIG. 6C;

FIG. 7 is a perspective view of a connector for attaching a rod to atether, the connector having a side-loading rod slot; and

FIG. 8 is a perspective view of a connector for attaching a rod to atether, the connector having a top-loading rod slot.

DETAILED DESCRIPTION

Systems and methods for reducing the risk of PJK, PJF, and otherconditions are disclosed herein. In some embodiments, a longitudinalextension can be added to a primary fixation construct to extend theconstruct to one or more additional vertebral levels. The extension canbe attached to a first attachment point, such as a bone anchor implantedin a vertebra that is superior to the primary construct. The extensioncan also be attached to a second attachment point, such as a componentof the primary construct or an anatomical structure disposed inferior tothe first attachment point. The extension can be more flexible than theprimary construct and/or can limit motion to a lesser degree than theprimary construct, thereby providing a more-gradual transition from theinstrumented vertebrae to the natural patient anatomy adjacent thereto.The extension can be placed with little or no soft tissue disruption.

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the systems and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the systems andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments.

FIGS. 2A-2B schematically illustrate a system and method for treating,preventing, or reducing the risk of proximal junctional kyphosis,proximal junctional failure, and other conditions. As shown, a primaryconstruct 200 can be implanted in a patient and attached to thepatient's spine S. The primary construct 200 can be extended to one ormore additional vertebral levels by (i) attaching a longitudinalextension 202 to a first attachment point 204, (ii) positioning thelongitudinal extension relative to the patient's spine, and (iii)attaching the longitudinal extension to a second attachment point 206.The first attachment point 204 can be an implant or an anatomicalstructure that is longitudinally offset from the primary construct 200,e.g., one or more vertebral levels superior to the UIV of the primaryconstruct. The extension 202 can be attached to the first attachmentpoint 204 in a manner that does not disrupt or only minimally disruptssoft tissue in the vicinity of the first attachment point. The secondattachment point 206 can be an implant or an anatomical structuredisposed at or below the UIV of the primary construct 200. For example,the second attachment point can be a rod 208, bone anchor 210, or othercomponent of the primary construct 200 itself, or a vertebra to whichthe primary construct is attached. The above steps can be performed inany sequence. For example, the extension 202 can be implanted prior tothe primary construct 200. As another example, the extension 202 can beattached to the first attachment point 204 after placing the extensionin its final position relative to the spine and/or after attaching theextension to the second attachment point 206.

The extension can provide a step-down in stiffness and/or spinal motionrestriction between the primary construct (which is typically relativelyrigid and immobile) and the natural soft tissue and other patientanatomy superior to the primary construct (to which there is generallyno implant-based rigidity or mobility restriction applied). Theextension can have a stiffness that is greater than the natural patientanatomy and less than the primary construct. The extension can have adegree of spinal motion restriction that is greater than the naturalpatient anatomy and less than the primary construct. The extension canhelp insulate the patient anatomy superior to the primary construct fromforces and stress that may contribute to PJK/PJF. The extension canprovide a soft link between the primary construct and undisturbed softtissue superior thereto. The extension can constrain or limit flexion ofthe spine to reduce the risk of PJK/PJF. The extension can replicate thenatural soft tissue envelope. In some embodiments, the vertebraeinstrumented with the primary construct are fused to one another and thevertebrae to which the primary construct is extended by the extensionare not fused. Accordingly, a hybrid construct can be formed in which afirst spinal segment is instrumented and fused, a second spinal segmentsuperior to the first segment is instrumented and not fused, and a thirdspinal segment superior to the second segment is neither instrumentednor fused.

Referring now to FIG. 2B, in a step S1, a primary construct can beimplanted in the patient. The primary construct can include one or morespinal rods extending longitudinally along the patient's spine. Thespinal rod or rods can be attached to the patient's spine using boneanchors such as pedicle or lateral mass screws, hooks, wires, and soforth. The primary construct can extend along a segment of the spinebetween an uppermost instrumented vertebra (UIV) of the primaryconstruct, i.e., the most-superior or most-cranial vertebra to which theprimary construct is attached, and a lowermost instrumented vertebra(LIV) of the primary construct, i.e., the most-inferior or most-caudalvertebra to which the primary construct is attached. The UIV can be theuppermost vertebra in which a bone screw of the primary construct isimplanted. The LIV can be the lowermost vertebra in which a bone screwof the primary construct is implanted. The primary construct can beimplanted using any of a variety of known techniques, including openprocedures, minimally-invasive or percutaneous procedures, and so forth.The primary construct can be implanted through a primary incision. Theprimary incision can extend longitudinally along the patient's spine.The terminal superior end of the primary incision can be locatedinferior to UIV+1, inferior to UIV, and/or inferior to UIV−1. Theprimary incision can include a plurality of discrete incisions, e.g., inthe case of minimally-invasive procedures for installing the primaryconstruct. The primary construct can include a rigid spinal rod, e.g., arod that does not materially bend or deform post-implantation whensubjected to normal anatomical loads, or a rod which is not designed tobend or deform under such conditions.

In a step S2, a longitudinal extension can be attached to a firstattachment point, e.g., a location within the patient that is offsetfrom the primary construct. The extension can be or can include any of avariety of elements for extending the primary construct to one or moreadditional vertebral levels. For example, the extension can be a tether,cable, cord, mesh, fabric, tape, film, or wire. The extension can beflexible. The extension can have a stiffness that is less than that ofthe primary construct or a component thereof, e.g., less than astiffness of a spinal rod of the primary construct. The extension canhave a stiffness that is greater than that of the natural spinalanatomy, e.g., greater than that of the ligaments and other soft tissuethat connect the vertebrae.

The extension can be a length of MERSILENE tape available from ETHICONof Somerville, N.J. The extension can be a length of non-absorbable,braided, sterile material. The extension can be formed from poly(ethylene terephthalate). The extension can be formed from fibers ofhigh molecular weight, long-chain, linear polyesters having recurrentaromatic rings. The extension can be coated with anti-bacterial agents,corticosteroids, anti-infective agents, tryclosan, and so forth. Theextension can be radiopaque, radiolucent, or partially radiopaque andpartially radiolucent. The extension can include imaging bands ormarkers. The extension can be polymeric. The extension can be formedfrom or can include various materials including polyethyleneterephthalate or DACRON, polytetrafluoroethylene or TEFLON,poly-praraphenylene terephthalamide or KEVLAR,ultra-high-molecular-weight polyethylene (UHMWPE), nylon, poly(L-lacticacid), and the like. The extension can be reinforced with materialsincluding metals, elastomers, carbon fibers, etc. The extension caninclude resilient or shape memory materials such as elastomers ornitinol. Such materials can allow the extension to not only limitflexion of the spine, but also to instill extension forces, which mayimprove lordosis and/or reinforce posterior soft tissues. The extensionforces can be tailored based upon material properties, weavingstructure, thickness, or other attributes of the extension.

The extension can be a tether that is substantially flat or planar. Thetether can have a cross-sectional width that is greater than across-sectional height. For example, the width can be at least two timesgreater than the height. The width of the tether can be in the range ofabout 4 mm to about 8 mm. The height of the tether can be in the rangeof about 0.5 mm to about 2.5 mm. The tether can have any number ofdifferent cross-sections, including rectangular, square, elliptical,circular, and so forth.

The extension can be attached to a first attachment point that is offsetfrom the primary construct, e.g., one or more vertebral levels superiorto the primary construct. The first attachment point can be a vertebra.The first attachment point can be a pedicle, a transverse process, alamina, a facet, a spinous process, or a vertebral body of the vertebra.The first attachment point can be an implant implanted in any of theabove locations. The vertebra can be superior to UIV. The vertebra canbe UIV+1, UIV+2, or higher. The first attachment point can be a rib orother anatomical anchor point. The first attachment point can be a bonestructure. The first attachment point can be a soft tissue structure.The first attachment point can be a muscle, a tendon, or a ligament. Theextension can be attached to a plurality of the above-described firstattachment points.

The extension can be attached to the first attachment point in any of avariety of ways. The extension can be attached to the first attachmentpoint using a suture, rivet, or staple. The extension can be attached tothe first attachment point using a clamp. The clamp can be attached to alamina, spinous process, or other anatomical structure or implant. Theextension can be attached to the first attachment point using a hook.The hook can be hooked onto a lamina, spinous process, or otheranatomical structure or implant. The extension can be attached to thefirst attachment point using a bone anchor, e.g., a screw anchor, asuture anchor, an expandable anchor, a tether anchor, and/or asoft-tissue anchor, any of which may be of the type available from DEPUYSYNTHES of Raynham, Mass.

The extension can be attached to the first attachment point in a waythat minimizes soft tissue disruption. The extension can be positionedat the first attachment point without extending the primary incisionand/or without forming any incision other than the primary incision. Theextension can be positioned at the first attachment point through asmall secondary incision formed over the first attachment point. Thesecondary incision can be percutaneous stab incision. The secondaryincision can be made only as large as necessary to pass the extensiontherethrough, or only as large as necessary to pass an anchor forattaching the extension therethrough. The secondary incision can have alength that is equal or substantially equal (e.g., within 10% of) acorresponding dimension of the extension. The secondary incision canhave a diameter that is equal or substantially equal (e.g., within 10%of) a diameter of a bone anchor used to attach the extension to thefirst attachment point. The secondary incision can have a length ordiameter that is less than about 10 mm, less than about 5 mm, less thanabout 3 mm, and/or less than about 1 mm. The extension, or at least oneend thereof, the anchor, or both the extension and the anchor, can bedelivered to the first attachment point through a trocar, tube, orcannula. The extension can be attached to the first attachment pointwithout disturbing the soft tissue envelope of the vertebral levelssuperior to the primary construct.

In a step S3, the extension can be positioned relative to the patient'sspine. The extension can be positioned to extend along the patient'sspine between the first attachment point and a second attachment point,such as the primary construct.

The extension can be passed through the secondary incision and thenpushed and/or pulled in an inferior direction towards the primaryconstruct, passing the extension beneath the skin and/or soft tissuedisposed intermediate to the secondary incision and the primaryconstruct. The extension can be pushed and/or pulled in the inferiordirection by an inserter or tunneling instrument. The inserterinstrument can be passed through the primary incision and up towards thesecondary incision to grab the extension before pulling it inferiorly.The inserter instrument can be passed through the secondary incision andpushed with the extension coupled thereto inferiorly towards the primaryconstruct, beneath the skin and/or soft-tissue.

The extension can be inserted through the primary incision and passed ina superior direction towards the first attachment point, guiding theextension beneath the skin and/or soft tissue disposed intermediate tothe first attachment point and the primary incision. The extension canbe passed in the superior direction using forceps, a pushrod, or otherinserter instrument.

The extension can be positioned along a posterior aspect of the spine.The extension can be positioned along an anterior or lateral aspect ofthe spine. The extension can be positioned such that no portion of theextension is disposed anterior to any lamina of the patient's spine.

The extension can be positioned in a way that minimizes soft tissuedisruption. The extension can be positioned without extending theprimary incision and/or without forming any incision other than theprimary incision. The extension can be positioned without disturbing thesoft tissue envelope of the vertebral levels superior to the primaryconstruct.

In a step S4, the extension can be attached to a second attachmentpoint. The second attachment point can be inferior to the firstattachment point. The second attachment point can be a spinal rod, abone anchor or bone screw, a cross-connector, or any other component ofthe primary construct. The second attachment point can be an anatomicalstructure adjacent or inferior to the primary construct.

The second attachment point can be a vertebra. The second attachmentpoint can be a pedicle, a transverse process, a lamina, a facet, aspinous process, or a vertebral body of the vertebra. The secondattachment point can be an implant implanted in any of the abovelocations. The vertebra can be inferior to the UIV of the primaryconstruct. The vertebra can be UIV, UIV−1, UIV−2, or lower. The secondattachment point can be a rib or other anatomical anchor point. Thesecond attachment point can be a bone structure. The second attachmentpoint can be a soft tissue structure. The second attachment point can bea muscle, a tendon, or a ligament. The extension can be attached to aplurality of the above-described second attachment points.

The extension can be attached to the second attachment point in any of avariety of ways. The extension can be attached to the second attachmentpoint using a suture, rivet, or staple. The extension can be attached tothe second attachment point using a clamp. The clamp can be attached toa lamina, spinous process, or other anatomical structure or implant. Theextension can be attached to the second attachment point using a hook.The hook can be hooked onto a lamina, spinous process, or otheranatomical structure or implant. The extension can be attached to thesecond attachment point using a bone anchor, e.g., a screw anchor, asuture anchor, an expandable anchor, a tether anchor, and/or asoft-tissue anchor, any of which may be of the type available from DEPUYSYNTHES of Raynham, Mass.

The second attachment point can be a spinal rod. The extension can beattached to the spinal rod using a clamp or connector that receives therod and the extension.

The second attachment point can be a bone anchor, e.g., a screw or ahook. The extension can be attached to the bone anchor using a clamp orconnector that receives the bone anchor and the extension. The extensioncan be clamped between a spinal rod and a rod seat of the bone anchor.The extension can be clamped between a spinal rod and a set screw orclosure mechanism of the bone anchor. The bone anchor can include afirst set screw or closure mechanism for locking the extension to thebone anchor and a second set screw or closure mechanism for locking aspinal rod to the bone anchor.

The above steps can be repeated to attach multiple extensions to thepatient's spine. The multiple extensions can share common attachmentpoints or can be attached at different locations. For example, first andsecond extensions can be placed in parallel on contralateral sides ofthe spinal midline. Inferior ends of the extensions can be attached torespective spinal rods and/or respective bone anchors of a primaryconstruct. Superior ends of the extensions can be attached to respectiveattachment points longitudinally offset from the primary construct, orto a common attachment point such as a spinous process of a superiorvertebra.

FIGS. 3A-3E illustrate an example of the systems and methods describedabove. In FIG. 3A, a primary construct 300 is implanted in a patientusing known techniques. The primary construct 300 can be implantedthough a primary incision 312. The primary construct 300 can includefirst and second spinal rods 308 coupled to the patient's vertebrae byrespective bone anchors 310. Only the UIV of the primary construct 300is shown, though it will be appreciated that the primary construct canextend inferiorly to one or more additional vertebrae. As also shown inFIG. 3A, a screw-type bone anchor 314 with a flexible tether 302attached thereto can be driven into a vertebra superior to the primaryconstruct 300, e.g., UIV+1 as shown. The tether 302 can serve as alongitudinal extension and the anchor 314 can define the firstattachment point 304. The anchor 314 can be delivered and/or driven intothe bone with a driver instrument 316. The driver instrument 316 candefine a central passage in which the tether 302 can be stored duringanchor insertion. The anchor 314 can be delivered through a smallsecondary incision 318 disposed superior to the primary incision 312with little or no disruption to the soft tissue envelope. The anchor 314can include a threaded bone-engaging portion. The anchor 314 can includean inner lumen in which at least a portion of the tether 302 isdisposed.

As shown in FIG. 3B, after driving the anchor 314 into bone, the driverinstrument 316 can be withdrawn proximally, leaving the tether 302extending from the anchor 314, with the anchor 314 now serving as afirst attachment point 304. The tether 302 can extend through thesecondary incision 318 to a location external to the patient. The tether302 can be fixed to the anchor 314 or can be threaded or looped throughan aperture formed in the anchor or around a post disposed in a lumen ofthe anchor.

As shown in FIG. 3C, an inserter or tunneling instrument 320 can bepassed through the secondary incision 318 and pushed inferiorly towardsthe primary incision 312 through or beneath the patient's skin and/orsoft tissue 322. The inserter instrument 320 can be rigid or semi-rigidto facilitate pushing of the instrument through the patient. Theinserter instrument 320 can include a hook, aperture, or otherattachment 324 for attaching the inserter instrument to the tether 302.The attachment 324 can be disposed at or near a proximal or trailing endof the inserter instrument 320. The leading end of the inserterinstrument 320 can be pushed through the secondary incision 318 andtowards the primary incision 312. A user can then reach into the primaryincision 312, grasp the leading end of the inserter instrument 320, andpull the inserter instrument through the primary incision.

As shown in FIG. 3D, the tether 302 can be pulled along the same path asthe inserter instrument 320, thereby positioning the tether such that itextends along the patient's spine between the first attachment point 304and the primary construct 300.

As shown in FIG. 3E, the tether 302 can be attached to the primaryconstruct 300 or to another second attachment point 306. For example,the tether 302 can be tied off to the primary construct 300 or, asshown, a tether-to-rod connector 326 can be used to attach the tether toa spinal rod 308 of the primary construct. Any excess length of thetether 302 can be cut off and discarded.

It will be appreciated that the above method can be varied in numerousways. For example, as shown in FIG. 4, an extension 402 with a hook 428mounted thereto, e.g., at a terminal end thereof, can be passedsuperiorly from the primary incision 412 to the first attachment point404, beneath the skin and/or soft tissue of the patient. The hook 428can be hooked onto any of a variety of anatomical structures of thepatient, such as a lamina of UIV+1 as shown or of a more-superiorvertebra. In such a method, the need for a secondary incision and/or abone anchor can be eliminated. By way of further example, as shown inFIG. 5, an extension 502 with a clamp 530 mounted thereto, e.g., at aterminal end thereof, can be passed superiorly from the primary incision512 to the first attachment point 504, beneath the skin and/or softtissue of the patient. The clamp 530 can be clamped onto any of avariety of anatomical structures of the patient, such as a lamina ofUIV+2 as shown, of a more-superior vertebra, or of UIV+1. In such amethod, the need for a secondary incision and/or a bone anchor can beeliminated. The clamp 530 can include opposed jaws that are biasedtowards one another, e.g., by a spring.

FIGS. 6A-6E illustrate an exemplary connector 600 that can be used inthe above methods to attach the extension to the primary construct. Forexample, the connector 600 can be used to attach a spinal rod of theprimary construct to an elongate flexible tether or other type ofextension.

As shown, the connector 600 can include a body 602 that defines a tetherslot or channel 604 and a rod slot or channel 606. The connector 600 canalso include a locking element or set screw 608 that can be actuated tolock the connector 600 to a tether 610 and to a rod 612. The connector600 can allow for simultaneous locking to the tether 610 and to the rod612.

The body 602 can include proximal and distal ends 602 p, 602 d thatdefine a central proximal-distal axis A1. The body 602 can includeopposed end walls 614, 616, a vertical sidewall 618, and proximal anddistal arms 620, 622 extending laterally from the vertical sidewall. Thearms 620, 622 can define the rod slot 606 therebetween. At least aportion of the tether slot 604 can also be defined between the arms 620,622. A rod 612 disposed in the rod slot 606 can have a centrallongitudinal rod axis A2. The rod slot 606 can be open in a lateraldirection, such that a rod can be inserted into the rod slot by movingthe rod laterally with respect to the connector 600 or vice versa. Eachof the arms 620, 622 can extend from the vertical sidewall 618 to a freeend. The body 602 can thus be C-shaped in a plane perpendicular to therod axis A2.

The tether slot 604 can extend from an opening 624 formed in the endwall 614 of the distal arm 622, through a first tunnel 626 formed in thedistal arm, across a proximal-facing clamping surface 628 of the distalarm, through a second tunnel 630 formed in the distal arm, and to anopening 632 formed in the opposite end wall 616 of the distal arm. Theclamping surface 628 can include grooves, ridges, teeth, or otherfeatures for enhancing grip or friction between the connector 600 and atether 610 disposed in the tether slot 604. The first and second tunnels626, 630 can extend at an oblique angle with respect to the axis A1, theaxis A2, and/or the clamping surface 628. The first and second tunnels626, 630 can extend in a distal-to-proximal direction as they approachthe axis A1. The first and second openings 624, 632 and/or the first andsecond tunnels 626, 630 can have a cross-section in a planeperpendicular to the axis A2 that substantially corresponds to that ofthe tether 610, e.g., a substantially rectangular cross-section.

The proximal arm 620 can include an opening 634 configured to receivethe set screw 608. The opening 634 can include interior threads thatengage with an exterior thread of the set screw 608. Accordingly, theset screw 608 can move along the axis A1 by rotating the set screw aboutthe axis A1 relative to the body 602. While a set screw 608 is shown, itwill be appreciated that other locking elements can be used instead oraddition, such as a closure cap that advances and locks by quarter-turnrotation, a closure cap that slides in laterally without rotating, athreaded nut, and so forth.

In use, a tether 610 can be positioned within the tether slot 604 and arod 612 can be positioned within the rod slot 606. The tether 610 can bepulled through the tether slot 604 until the desired tension is appliedto the patient's spine. The set screw 608 can then be tightened toadvance the set screw distally relative to the body 602 and to urge therod 612 towards the clamping surface 628, thereby clamping the tether610 between the rod and the clamping surface. When the set screw 608 istightened, the rod 612 can be locked to the connector 602 such that therod cannot rotate or translate relative to the connector. Similarly,when the set screw 608 is tightened, the tether 610 can be locked to theconnector 600 such that the tether cannot rotate or translate relativeto the connector.

FIG. 7 illustrates another exemplary connector 700 that can be used inthe above methods to attach the longitudinal extension to the primaryconstruct. For example, the connector 700 can be used to attach a spinalrod of the primary construct to an elongate flexible tether or othertype of extension.

As shown, the connector 700 can include a body 702 that defines a tetherslot or channel 704 and a rod slot or channel 706. The connector 700 canalso include a first locking element or set screw 708A that can beactuated to lock the connector 700 to a tether and a second lockingelement or set screw 708B that can be actuated to lock the connector toa rod. The connector 700 can allow for independent locking to the rodand to the tether.

The body 702 can include proximal and distal ends 702 p, 702 d thatdefine a central proximal-distal axis A1.

The body 702 can include a first portion 736 with opposed arms thatdefine the tether slot 704 therebetween. The arms can include interiorthreads or can be otherwise configured to mate with the first lockingelement 708A. A tether clamping surface 738 can be defined between theopposed arms. The clamping surface 738 can include grooves, ridges,teeth, or other features for enhancing grip or friction between theconnector 700 and a tether disposed in the tether slot 704. The tetherslot 704 can be open in a proximal direction, such that a tether can beinserted into the slot by moving the tether distally with respect to theconnector 700. A tether disposed in the tether slot can extend along atether axis A2. The axis A2 can be perpendicular to the axis A1.

The body 702 can include a second portion 740 with opposed arms thatdefine the rod slot 706 therebetween. The proximal arm can include athreaded recess 734 or can be otherwise configured to mate with thesecond locking element 708B. A rod clamping surface 742 can be definedbetween the opposed arms. The rod slot 706 can be open in a lateraldirection, such that a rod can be inserted into the slot by moving therod laterally with respect to the connector 700. A rod disposed in therod slot 706 can extend along a rod axis A3. The axis A3 can beperpendicular to the axis A1. The axis A3 can be parallel to the axisA2.

The body 702 can have a UC-shape in a plane perpendicular to the tetheraxis A2 and the rod axis A3.

While first and second set screws 708A, 708B are shown, it will beappreciated that other locking elements can be used instead or addition,such as a closure cap that advances and locks by quarter-turn rotation,a closure cap that slides in laterally without rotating, a threaded nut,and so forth.

In use, a tether can be positioned within the tether slot 704 and a rodcan be positioned within the rod slot 706. The first and second setscrews 708A, 708B can be tightened to lock the tether and the rod to oneanother and to the connector 700. The first and second set screws 708A,708B can be tightened in any sequence, and can allow for independentlocking of the rod and the tether to the connector 700. Prior tolocking, the tether can be pulled through the tether slot 704 until thedesired tension is applied to the patient's spine. The first set screw708A can be tightened to advance the set screw distally relative to thebody 702 and to clamp the tether against the tether clamping surface738. When the first set screw 708A tightened, the tether can be lockedto the connector 700 such that the tether cannot rotate or translaterelative to the connector. The second set screw 708B can be tightened toadvance the second set screw distally relative to the body 702 and toclamp the rod against the rod clamping surface 742. When the second setscrew 708B is tightened, the rod can be locked to the connector 700 suchthat the rod cannot rotate or translate relative to the connector.

FIG. 8 illustrates another exemplary connector 800 that can be used inthe above methods to attach the longitudinal extension to the primaryconstruct. For example, the connector 800 can be used to attach a spinalrod of the primary construct to an elongate flexible tether or othertype of extension.

The connector 800 can be substantially similar to the connector 700described above. For example, the connector 800 can include a body 802with a central proximal-distal axis A1, a first portion 836 that definesa tether slot 804, a second portion 840 that defines a rod slot 806, andfirst and second set screws 808A, 808B for securing a tether and a rod,respectively to the connector 800. The connector 800 can differ from theconnector 700 in that the rod slot 806 can be open in a proximaldirection such that the connector 800 has a UU-shape in a planeperpendicular to the tether axis A2 and the rod axis A3. Also, thesecond set screw 808B of the connector 800 can be received between theopposed arms of the second portion 840 of the connector, as opposed to arecess 734 formed in a single arm as in the connector 700. The structureand operation of the connector 800 can be otherwise the same as that ofthe connector 700.

It should be noted that any ordering of method steps expressed orimplied in the description above or in the accompanying drawings is notto be construed as limiting the disclosed methods to performing thesteps in that order. Rather, the various steps of each of the methodsdisclosed herein can be performed in any of a variety of sequences. Inaddition, as the described methods are merely exemplary embodiments,various other methods that include additional steps or include fewersteps are also within the scope of the present disclosure.

While extension of a construct in a superior direction is generallydescribed above, it will be appreciated that the systems and methodsdisclosed herein can also be used to extend a construct in an inferiordirection, or solely within the superior and inferior limits of aprimary construct, e.g., to reinforce the primary construct.

While the systems and methods disclosed herein are generally describedin the context of spinal surgery with rigid spinal fixation constructs,it will be appreciated that the systems and methods herein can be usedwith various other types of fixation or stabilization hardware, in anybone, in non-bone tissue, or in non-living or non-tissue objects. Thesystems disclosed herein and the various component parts thereof can befully implanted, or can be used as part of an external fixation orstabilization system. The systems and methods disclosed herein can beused in minimally-invasive surgery and/or open surgery.

The systems disclosed herein and the various component parts thereof canbe constructed from any of a variety of known materials. Exemplarymaterials include those which are suitable for use in surgicalapplications, including metals such as stainless steel, titanium,cobalt-chromium, titanium-molybdenum, or alloys thereof, polymers suchas PEEK, ceramics, carbon fiber, and so forth. The various components ofthe systems disclosed herein can be rigid or flexible. One or morecomponents or portions of the system can be formed from a radiopaquematerial to facilitate visualization under fluoroscopy and other imagingtechniques, or from a radiolucent material so as not to interfere withvisualization of other structures. Exemplary radiolucent materialsinclude carbon fiber and high-strength polymers.

Although specific embodiments are described above, it should beunderstood that numerous changes may be made within the spirit and scopeof the concepts described.

1. A surgical method comprising: attaching a primary construct to aspine of a patient, the primary construct extending between an uppermostinstrumented vertebra (UIV) and a lowermost instrumented vertebra (LIV);attaching a flexible longitudinal extension to a first attachment point,the first attachment point being disposed superior to the UIV of theprimary construct; positioning the extension relative to the patient'sspine; and attaching the extension to a second attachment point, thesecond attachment point being disposed at or inferior to the UIV of theprimary construct.
 2. The method of claim 1, wherein the firstattachment point comprises a bone anchor implanted in a vertebradisposed superior to the UIV of the primary construct.
 3. The method ofclaim 1, wherein the first attachment point is at least two vertebrallevels superior to the UIV of the primary construct.
 4. The method ofclaim 1, wherein the second attachment point comprises a rigid spinalrod of the primary construct.
 5. The method of claim 1, wherein theextension has a stiffness that is greater than a stiffness of patientanatomy superior to the UIV of the primary construct and that is lessthan a stiffness of the primary construct.
 6. The method of claim 1,wherein the extension has a degree of spinal motion restriction that isgreater than that of patient anatomy superior to the UIV of the primaryconstruct and less than that of the primary construct.
 7. The method ofclaim 1, wherein the extension limits flexion of the spine withoutcompletely preventing such flexion.
 8. The method of claim 1, whereinvertebrae instrumented with the primary construct are fused to oneanother or prepared for such fusion and vertebrae to which the primaryconstruct is extended by the extension are not fused or prepared forfusion.
 9. The method of claim 1, wherein the primary constructcomprises a rigid spinal rod attached to first and second vertebrae byrespective bone anchors.
 10. The method of claim 1, further comprisingforming a primary incision through which the primary construct isimplanted.
 11. The method of claim 10, wherein the primary incisionterminates at a location inferior to a vertebra (UIV+1) that issuperior-adjacent to the UIV of the primary construct.
 12. The method ofclaim 1, wherein the extension comprises a polymeric tether.
 13. Themethod of claim 1, wherein the extension exerts extension forces on thepatient's spine.
 14. The method of claim 1, wherein the first attachmentpoint is a rib.
 15. The method of claim 1, wherein the first attachmentpoint is a soft tissue structure of the patient.
 16. The method of claim1, wherein the extension is attached to the first attachment point by ahook or a clamp.
 17. The method of claim 1, wherein the extension isattached to the first attachment point by a bone anchor through whichthe extension is threaded.
 18. The method of claim 1, wherein attachingthe extension to the first attachment point comprises driving a boneanchor into bone with the extension extending from the bone anchor andthrough a shaft of a driver instrument.
 19. The method of claim 1,wherein positioning the extension comprises passing the extensionthrough a secondary incision disposed superior to a primary incisionthrough which the primary construct is implanted.
 20. The method ofclaim 19, wherein positioning the extension comprises passing theextension through the secondary incision and then pushing and/or pullingthe extension in an inferior direction towards the primary construct,passing the extension beneath the skin and/or soft tissue disposedintermediate to the secondary incision and the primary construct. 21.The method of claim 19, wherein positioning the extension comprisespassing an inserter instrument through the primary incision in asuperior direction towards the secondary incision, contacting theextension with the inserter instrument, and pulling the extension in aninferior direction using the inserter instrument.
 22. The method ofclaim 19, wherein positioning the extension comprises passing aninserter instrument through the secondary incision, coupling theextension to the inserter instrument, and pushing the inserterinstrument and the extension coupled thereto in an inferior directiontowards the primary construct, beneath the skin and/or soft-tissuedisposed intermediate to the secondary incision and the primaryconstruct.
 23. The method of claim 1, wherein positioning the extensioncomprises inserting the extension through a primary incision throughwhich the primary construct is implanted, and passing the extension in asuperior direction towards the first attachment point while guiding theextension beneath the skin and/or soft tissue disposed intermediate tothe first attachment point and the primary incision.
 24. The method ofclaim 1, wherein the extension is attached to the second attachmentpoint by a connector.
 25. The method of claim 24, wherein the connectorclamps the extension to a spinal rod or a bone screw of the primaryconstruct.
 26. The method of claim 1, wherein the extension comprises afirst extension and wherein the method further comprises placing asecond extension on a contralateral side of the spinal midline from thefirst extension.
 27. The method of claim 1, wherein positioning theextension comprises passing the extension superiorly from a primaryincision through which the primary construct is implanted to the firstattachment point, the extension passing beneath the skin and/or softtissue of the patient, and wherein attaching the extension to the firstattachment point comprises hooking a hook attached to the extension ontothe first attachment point or clamping a clamp attached to the extensiononto the first attachment point.
 28. The method of claim 1, wherein noportion of the extension is disposed anterior to any lamina of thepatient's spine when the extension is attached to the first and secondattachment points.
 29. A surgical method, comprising: forming a primaryincision in a patient; attaching a primary construct to the patient'sspine via the primary incision; forming a secondary incision in thepatient at a location superior to the primary incision; inserting a boneanchor through the secondary incision with an elongate flexible tetherattached to the bone anchor; driving the bone anchor into bone at afirst attachment point, thereby attaching the tether to the firstattachment point while a portion of the tether extends through thesecond incision to a location outside the patient; tunneling the tetherbeneath soft tissue disposed intermediate to the primary incision andthe secondary incision; and attaching the tether to the primaryconstruct via the primary incision.
 30. The method of claim 29, whereintunneling the tether comprises inserting an inserter instrument throughthe secondary incision and pushing the instrument inferiorly towards theprimary incision.
 31. The method of claim 30, further comprisinggrasping a leading end of the inserter instrument via the primaryincision and pulling the inserter instrument through the primaryincision.
 32. The method of claim 30, wherein the tether is attached tothe inserter instrument and is carried along the same path as theinserter instrument, thereby positioning the tether such that it extendsalong the patient's spine between the first attachment point and theprimary construct.
 33. A surgical system, comprising: a primaryconstruct comprising a rigid spinal fixation rod and first and secondbone anchors configured to attach the spinal rod to first and secondvertebrae; an elongate flexible tether attached to a tether anchor; adriver instrument for driving the tether anchor into bone while thetether extends from the tether anchor; and a connector configured toclamp the tether to the spinal rod of the primary construct.